The present disclosure is concerned with three-dimensional (3D) printing of polymers. Collagen is an example of a biological hydrogel polymer and is an important component of bones, teeth, and other tissues, for example. A two-stage chemical process can be used to transform collagen into hardened tooth mineral by cyclic immersion in calcium and phosphate salt solutions, followed by maturation in a buffered solution at constant temperature and pH. While this technology can create such biomaterials, it is not capable of forming them into a defined structure, like a human tooth, for example. Additionally, the process is time-consuming, laborious, and to date has only been performed on amorphous collagen samples.